wadecool

Wow, this thread has really taken on a life of its own. I'm guessing since nobody has said anything about my original question, I'll just do without. If I ever figure out a way to do it, I'll let you guys know.

XLR8R

If there's enough interest in a kit like that - I'm sure we'll have one on the '05 by the end of the season.

Mglass1045

Wade try this. Looks kinda like what you are after.

http://autospeed.drive.com.au/cms/A_2188/article.html

jrs_dodge_diesel

Lets say for example that you are accelerating hard and your boost pressure is 25 PSI. Now say for some reason you have to let off the pedal quick. The turbo is still spinning and feeding that 25 PSI to the cylinders, which now no longer need that 25 PSI. So now we have an intake at 25 PSI. Well, that pressure must equalize. It can only go one of two ways. Into the engine (not going to happen since the engine doesn't need it), or back out through the intake. The compressor turbine (still spinning) now reaches a point where it can no longer force that 25 PSI into the engine. Since these events are happing very rapidly, the excess pressure is forced to flow back out of the intake in the form of a pressure wave. This is when the compressor vanes stall, and rapidly decrease speed. As to why exactly it makes the stuttering noise is beyond me (maybe 600 MW knows that answer). Think of a turboprop airplane when the reverse the pitch of the props, makes a very distinct sound due to the change in airflow across the blades, similar concept with our turbos.

For your other question, yes, the exhaust turbine and compressor are directly connected via a shaft. When turbo bark (compressor surge/stall) occurs, both the compressor and the exhaust turbine slow down rapidly. But the neither the shaft or turbines will stop, or spin backward. At idle there is still exhaust flowing out the manifold, so once the turbo bark nears the end of its cycle, the turbo will return to its idle speed.

Wade,

I have come up with an idea that may work, and be cheap at the same time (LanceD has heard this before ). It involves a toggle switch, a microswitch, some wiring, and a 12V solenoid operated air valve. If you are interested let me know and I will draw up and post a schematic of what I have in mind.

wadecool

Jr, I'm definately interested in that schematic. I'd be nice to do something to the beast that won't cost a fortune.

inline6power

very well put, i just always thought and have always been told that the wheel and shaft either stop spinning or go into reverse spin for just a split second, but you explained it very well . thank you.

csutton7

jr --pretty much just diagnosed what happens---hard to push air where it won't go, so you have the two forces fighting each other and it makes your turbo bark/stall because the forces have to equal out and since you can't force that air through the engine the pressure equalizing happens at the turbo where the doggy is spinning and when that air comes back towards the spinning doggy and it doesn't like that and it barks---or maybe it farts or does both............


Kitchen--as stated your turbo isn't knocking your fuel out of the injectors, it's your right foot----I believe what's happening is that you're supplying a bunch of fuel and the injector pump is pumping for what it's worth and the engine is trying to consume all that fuel, but when you suddenly lift off the go pedal the pump stops pumping at its rapid rate but the engine is still doing its job, so when the fuel is reduced the pistons/valves are still doing their respective jobs (cuz the pump reacts faster than the pistons/valves)and the intake/exhaust forces sucks fuel out of the injector faster than the pump can replace it at this precise timing event---it all happens so quick, but you've gone to full out to full stop(kind of) according to what the pump sees, but the engine doesn't react as fast---ok now someone else chime in with their thoughts or at least put this in redneck terms--

I was trying to guzzle me a couple of cold ones right after one another, but the first one I finished before the 2nd one could be replaced and I swallowed some air and that's why I got the hiccups--sucked that first one dry sooner than the next one could replace it and them hiccups stopped me in my tracks----well kind of like this --there's better analogies, but since this is a public place I best not go there........
chris

LanceD

anyone have one of those high speed video cameras that they take pictures of bullets and explosions with? it would be nice to park one in front of the turbo and put it on a dyno. maybe get some proof on what happens. would be cool to watch too!

2500Ram

email Myth Busters

Ph4tty

You might be onto something.

Mglass1045

Man, I thought I was posting in invisible ink. This subject has been beaten to death by both sides on other posts. I like how BOVs sound, I think it'll help between shifts and it has to take some(all) the load off of the turbo. I don't see a down side other than $$. I've stumbled across some ideas that seem fairly reasonable $$ wise, but just haven't got around to it yet.

jrs_dodge_diesel

Here you go:



Very simple concept here. Install a toggle switch in the cab somewhere. This will be the main arming (enabling) switch, which will put power to the momentary switch. The momentary switch should be mounted either at the accelerator pedal, or at the throttle linkage on the injection pump (or APPS as the case may be) and be rigged so that the switch is closed (activated) whenever the pedal is released (idle). When both switches are closed that will apply voltage to the solenoid coil and open the air valve which will release any air pressure in the intake. The ideal place to install the air valve would be the intake horn i believe.

You want to have the main arming switch since you really don't need the BOV to be open every time the pedal is released, and could be a source of unfiltered air to come in the engine at idle.

If y'all have any questions please ask.

j_k_auto

Any update on this?

DMcPherson

first, to answer your question, someone, I beleive on this forum came up with running the vacuum source on the bov to the exhaust manifold, when off the throttle the dfference in pressure is enough to open the bov. just coil copper line from the manifold to the bov, viola.
Now, this debate has been beat to death and always makes me laugh. theres always someone jumping in to say that "barking" is ok and bov's are stupid.
If you can hear turbo surge than its bad. maybe it will not hurt anything, and keep doing it for years to come with no problems, or maybe the compressor wheel of your turbo will explode and take out your engine.
Diesels do not have as much need for a bov as a gas engine. but none the less if you can hear surge its bad. there is no mechanical stoppage like a throttle blade to create the reverberation or air back through the turbo, but it still happens.
As said previously, the wheels will not stop or spin backwards, but asking them to come down from 30-40 THOUSAND rpm so 5-10 in a fraction of a second i pretty demanding I would say. it doesnt need to stop or spin backwards to have a failure.
also as far as losing all your boost between gears. A lot of the time a bov will help to hold it as long as it is sized properly, instead of the turbo losing all of its speed and trying to pick it back up in the next gear, when a bov opens it allows the turbo to maintain speed and make it easier to come back up to boost.
Now have you ever wondered why those turbos are called phat shafts? because diesels generally use a larger impeller shaft to keep it from breaking during surge conditions.
ok, Im done. hopefully this was a constructive and useful post.

pokapotato

Whether the wheel slows almost to a stop or stops all together remains to be seen. I can provide an interesting prospective. I have seen first hand large Brown Bavary Turbos shear the shafts after large loads have been immediately take off. These were 2 Megawatt Caterpillar Diesel Generator Sets. You take the fuel away instantly, you take the driving force away from the turbo, that massive volume and pressure on the intake side come back and we have seen turbo shafts sheared. Leads me to believe that the compressor side is being brought to a stop. I can see a legitimate use for a blowoff valve on a diesel engine. I can't see that it would do me any good on my truck but maybe others are using their trucks in such a way.